The present invention relates to water faucets, and more particularly to a mixing water faucet structure that is presettable for selected proportions of hot and cold water and which prevents the backflow of water between the hot and cold water inlets thereof.
Presettable mixing faucets generally include a pair of separate setting valves for controlling the flow of hot and cold water, and an egress valve upstream therefrom which combines the hot and cold water into an efflux of desired temperature.
Substantial advantages are afforded over more conventional water faucets wherein the outflow of hot and cold water from corresponding valves is communicated directly to an egress spout without further control. Foremost of which, as the presettable type mixing faucet allows the prior adjustment of the setting valves for delivery of a hot and cold water mixture of desired proportion, a user would only have to actuate the egress valve which usually is of the on/off type to obtain an efflux of desired rate and temperature. Whereas, the conventional mixing faucet as described would require separate opening and adjustment of the hot and cold water valves therein upon each usage. Greater convenience and economy of time is thus achieved, especially in those applications best satisfied by a flow of constant rate and temperature, such as in a shower stall, flush tank, or plant irrigation system.
Furthermore, as only the egress valve needs to be actuated in the present type of mixing faucet to obtain emission, the rate of wear in the setting valves would accordingly be reduced in comparison with the corresponding hot and cold water valves in the conventional mixing faucet which would necessitate operation upon each occurence. Should the egress valve be of the on/off type the reliability of the system would be further increased due to their inherently greater sturdiness.
Referring to FIG. 1, a presettable water mixing faucet of the prior art is depicted comprising a housing 1, respective setting valves 2 and 2', a spout tube 3 connected to the water outlet 1a of housing 1, and a self-shutting egress valve 4 disposed in the free end of the spout tube 3.
Hot and cold water enters housing 1 through separate conduits in a combined water inlet 1b on a lower portion of the housing, and are combined in a mixing chamber 5 therein via setting valves 2 and 2'.
Each setting valve, 2 and 2', includes a positioning element 2a rotatably secured to an external position on housing 1, an attached shaft 2b, and a hollow valve piston 2c threadedly engaged with a tapped lower portion of shaft 2b. A turning knob 2d is secured over the positioning element to facilitate the rotation thereof and thereby effect axial displacement of valve piston 2c towards or away from a corresponding valve seat 2e formed within the housing. A valve washer 2f carried by valve piston 2c abuts the valve seat when the piston is at its maximum extension from shaft 2b to shut off the corresponding setting valve. Conversely, when piston 2c is in a fully retracted position the valve would be in a maximum flow setting.
By appropriate adjustments in valves 2 and 2' a mixture of hot and cold water of desired proportion will be formed in mixing chamber 5 for issuance through spout tube 3 when egress valve 4 is actuated.
The egress valve itself is of type including a sliding actuating plunger 4a disposed within a cup shaped cylinder 4b. The plunger acts as a valve piston and is biased towards a valve seat 4c provided below the cylinder by a spring 4d. The valve is operated by pushing plunger 4a upwards upon which water could then flow through a gap between an orifice 4e and the periphery thereof. Closure of the valve would be effected automatically by the fall of the plunger which, being viscously damped, would take several seconds.
Referring to FIG. 2, though this presettable mixing faucet structure can provide satisfactory results it does have a major deficiency in that with the egress valve in a closed position a backflow of water can occur between the hot water and cold water conduits as the setting valves are still in open positions, causing damage to the plumbing or heating system. Moreover, even if the hot and cold water lines were at substantially equal pressures an undesirable mixing of hot and cold water would result.
The mixing faucet of the present invention was accomplished to provide a faucet structure which prevents the backflow or premature mixing of hot and cold water therethrough while preserving all the functions and advantages of a more conventional presettable mixing faucet.